387-312 B.C.

Greek philosopher mistakenly credited with putting forth a heliocentric, or Sun-centered, model of the universe. Heraclides, who studied under Plato (427-347 B.C.) and Aristotle (384-322 B.C.), maintained that Venus was at times "above" or "below" the Sun—terminology a number of later scholars interpreted as meaning that the planets revolved around it. In fact he seems to have meant "ahead of" or "behind" the Sun, and it appears clear that he believed Earth to be at the center of the universe. He was, however, the first thinker to state that Earth rotates on its axis once daily.